The imaging speed of optical resolution photoacoustic microscopy (OR-PAM) using pulsed excitation is fundamentally limited by the range ambiguity condition, which defines the maximum laser pulse repetition frequency (PRF). To operate at this theoretical upper limit and maximize acquisition speed, a custom-built fiber laser capable of operating at a PRF of up to 2 MHz was combined with a fast laser scanning optical OR-PAM system based on a stationary fiber-optic ultrasound sensor. A large area (10 mm × 10 mm) of the mouse ear was imaged within 8 s, when acquiring 16 million A-lines and operating the laser at a PRF of 2 MHz. This corresponds to a factor of four improvement in imaging speed compared to the fastest OR-PAM system previously reported. The ability to operate at high-imaging frame rates also allows the capture of hemodynamic events such as blood flow. It is considered that this system offers opportunities for high throughput imaging and visualizing dynamic physiological events using OR-PAM.

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We report on high-energy nanosecond-pulsed fiber master oscillator power amplifier (MOPA) systems seeded by semiconductor laser diodes at 2 μm incorporating arbitrary pulse-shaping capabilities. Two MOPA systems, one based on direct diode modulation and the second using additional electro-optic modulator (EOM) based shaping, are investigated, with up to 0.5 mJ (25 kHz) and 1.0 mJ (12.5 kHz) pulse energies achieved, respectively, for 100 ns pulses with user-defined pulse shapes. Our results indicate that further energy scaling with shaped output pulses is primarily limited by the maximum pulse peak power available from the seed laser diode and the dynamic range offered by the first generation of EOMs at 2 μm.

Optical coherence tomography (OCT) imaging at the 1060-nm region proved to be a successful alternative in ophthalmology not only for resolving intraretinal layers, but also for enabling sufficient penetration to monitor the subretinal vasculature in the choroid when compared to most commonly used OCT imaging systems at the 800-nm region. To encourage further clinical research at this particular wavelength, we have developed a compact fiber-optic source based on amplified spontaneous emission (ASE) centered at 1060 nm with 70-nm spectral bandwidth at full-width at half-maximum and output power 20 mW. Our approach is based on a combination of slightly shifted ASE emission spectra from a combination of Neodymiumand Ytterbium-doped fibers. Spectral shaping and power optimization have been achieved using in-fiber filtering schemes. We have tested the performance of the source in an OCT system optimized for this wavelength.

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